Replacing Mixing Valve in a 2018 Tab 320-CS

MuttonChops

jalars8 said:
. . . Is the pin what I have been calling a piston?
. . . What is the wax seal for?
. . . How does it relate to the pin (or the piston) in the functioning of the element?

{ correct simple diagram showing 'pin' is not to scale.  I did not measure, 0.5in is a guess }

The wax thermostatic element is a two piece assembly.  "Pin" is what I called 'piston'.

The "wax-seal" (my name) is whatever is used to separate the wax and piston.
On my unit it had the white color seen in your picture.
The LG004X product diagram below shows the "wax-seal" as the Black layer in diagram.

Basic Theory of Operation:
   Wax is in the lower section, below the seal.
   Hot Water causes the wax to melt and expand.
   The wax can only expand upward, against the seal, which moves the piston/pin upward.
   When wax cools it goes back to solid state and shrinks; lowering seal & piston.
      (spring force when element is installed in LK550 forces the piston down)

jalars8

Thank you.  You are always a reliable source of information and I appreciate your help.